Photo: Jack Johnson was the first African American world heavyweight boxing champion. (AP)

US President Donald Trump has granted a rare posthumous pardon to boxing's first black heavyweight champion, clearing Jack Johnson's name more than 100 years after what many see as his racially charged conviction.

"I am taking this very righteous step, I believe, to correct a wrong that occurred in our history and to honour a truly legendary boxing champion," Mr Trump said during an Oval Office ceremony.

Johnson had served 10 months in prison, "for what many view as a racially motivated injustice", Mr Trump said.

"It's my honour to do it. It's about time," the President said.

Johnson, a prominent athlete who crossed over into popular culture decades ago with biographies, dramas and documentaries, was convicted in 1913 by an all-white jury for violating the Mann Act for traveling with his white girlfriend.

That law made it illegal to transport women across state lines for "immoral purposes".

Mr Trump had tweeted in late April that Stallone, a longtime friend, had brought Johnson's story to his attention in a phone call.

"His trials and tribulations were great, his life complex and controversial," Mr Trump wrote then.

"Others have looked at this over the years, most thought it would be done, but yes, I am considering a Full Pardon!"

After Johnson's conviction, he spent seven years as a fugitive, but eventually returned to the US and turned himself in.

He served about a year in federal prison and was released in 1921. He died in 1946 in a car accident.

The son of former slaves, Johnson defeated Tommy Burns for the heavyweight title in 1908 at a time when blacks and whites rarely entered the same ring.

He then beat a series of "great white hopes", culminating in 1910 with the undefeated former champion, James J Jeffries.

I agree Scepo. Donald Trump is, according to the left, incapable of anything good ... unlike their hero Barack "Did Nothing" Obama.

Perhaps they should read the following excerpt from Johnson's Wikipedia biography.

In April 2009, Senator John McCain, along with Representative Peter King, film maker Ken Burns and Johnson's great-niece, Linda Haywood, requested a presidential pardon for Johnson from President Barack Obama. In July of that year, Congress passed a resolution calling on President Obama to issue a pardon. In 2016, another petition for Johnson's pardon was issued by McCain, King, Senator Harry Reid and Congressman Gregory Meeks to President Obama, marking the 70th anniversary since the boxer's death.This time citing a provision of the Every Student Succeeds Act, signed by the president in December 2015, in which Congress expressed that this boxing great should receive a posthumous pardon, and a vote by the United States Commission on Civil Rights passed unanimously a week earlier in June 2016 to "right this century-old wrong." Mike Tyson, Harry Reid and John McCain lent their support to the campaign, starting a Change.org petition asking President Obama to posthumously pardon the world's first African-American boxing champion of his racially motivated 1913 felony conviction. Obama declined to pardon Johnson.